Stringed musical instrument backboard



FIG. 1 is a top plan view of a stringed musical instrument backboard showing my new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a right side elevational view, the opposite side being substantially a mirror image thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a lengthwise centerline sectional view thereof; and

FIG. 6 is a widthwise centerline sectional view thereof. 

The ornamental design for a stringed musical instrument backboard, substantially as shown and described. 